CA2216450C

CA2216450C - A spinal cage assembly

Info

Publication number: CA2216450C
Application number: CA002216450A
Authority: CA
Inventors: Peter Metz-Stavenhagen; Bernd Robioneck
Original assignee: Stryker Trauma GmbH
Current assignee: Stryker European Holdings I LLC
Priority date: 1996-09-26
Filing date: 1997-09-25
Publication date: 2004-05-25
Anticipated expiration: 2017-09-25
Also published as: EP0832622A3; DE69719431T2; EP0832622A2; JP3437916B2; EP0832622B1; DE69719431D1; ATE233523T1; CA2216450A1; US6193755B1; DE29616778U1; JPH1099356A

Abstract

The invention relates to a spinal cage assembly including a sleeve-shaped member of a metal compatible with the human body, said sleeve-shaped member having end faces defining irregular edges and having a wall provided with holes.

Description

A SPINAL CAGE ASSEMBLY
The present invention relates to a spinal cage assembly.
Spinal implants have become known which are formed as hollow members and which are inserted - individually or in pairs - into the area between adjacent vertebrae in order to obtain effective adherence between adjacent vertebrae.
Such implants are shown for example in European patent 0 307 741 B1, German patents 44 16 605 C1 and 43 23 956 C1, European patent application 0 637 440 A1, PCT-application WO 95/26164, US patent 5,015,247 and German utility model G 296 00 879. The hollow structure of the implants enables receival of bone material or the like for enhancing bone growth and adherence.
Furthermore so-called spinal cage assemblies have become known which are implanted for example after removal of a vertebra so as to replace the removed vertebra. Such spinal cage assemblies have become known for example from German utility model 91 07 494 and European patent applications 0 188 054 and 0 535 215. Such prior spinal cage assemblies engage the vertebrae in a substantially central area of relatively soft structure. Therefore, there is a risk of the spinal cage assembly "digging" into the vertebra.
A similar risk is present with spinal cage assemblies made of relatively thin wire mesh.
An object of the invention is to provide a spinal cage assembly allowing for effective support against and enabling growth of new bone substance between adjacent vertebrae.

la To this end the invention provides a spinal cage assembly comprising an external sleeve member and an internal sleeve member both of metal compatible with the human body, the external sleeve member being adapted to telescopically receive the internal sleeve member, the sleeve members having end faces defining irregular edges, the sleeve members including bores or holes to be aligned with each other and to receive threaded bolts for holding the sleeve members stationary with each other in different height positions.
The invention also provides a spinal cage assembly comprising an inner sleeve-shaped tubular body which telescopes into or through an outer tubular sleeve-shaped body, each inner and outer sleeve is of one-piece construction made of a physiologically compatible metal, wherein both sleeve-shaped bodies have multiple holes therein, and can be secured at different heights relative to one another, wherein at least one of the sleeve-shaped bodies has two edges which form a different angle of between about 3° and about 6° with respect to the transverse axis of the sleeve-shaped bodies such that an edge having a different angle is exposed depending on which end of said inner body is inserted into or through said outer body.
The spinal cage assembly of the present invention comprises a sleeve-shaped member of a material compatible with the human body. The sleeve-shaped member has a relatively thick wall suitable to receive and transfer substantial forces and en-abling engagement with adjacent vertebrae under relatively small surface pressure.
The support provided thereby is particularly effective when the diameter of the sleeve-shaped member is dimensioned such that the wall engages the vertebra in the cortical area thereof. As is known, the cortex is the hardest bone area.
In accordance with the invention the end faces or face edges of the sleeve-shaped member are of irregular shape. This prevents the sleeve-shaped member from rotary movements. Furthermore the wall of the sleeve-shaped member in-cludes windows through which bone material may be inserted into the interior of the sleeve-shaped member.
Preferably, the irregular edge of the sleeve-shaped member extends in a plane which is inclined to a transverse axis of the sleeve-shaped member under a prede-termined angle of e.g. 3 to 6°. This allows for adaption to different anatomic struc-tures.
The end face of the sleeve shaped member may be provided with teeth and gaps therebetween, with the tips of the teeth being formed as planar surfaces such as to prevent the spinal cage assembly from digging into the vertebrae.
Preferably, the gaps are of a round contour, with the gaps and the top surfaces of the teeth forming relatively sharp edges.
For assembly of a sleeve-shaped member a tool may be used, which has a relatively long shank and includes a threaded extension at a free end thereof.
The threaded extension may be engaged into a threaded bore of the sleeve-shaped mem-ber in order to insert the latter into the space of the removed vertebra in a predeterm-ined position between two adjacent vertebrae.
The height of the spinal cage assembly depends on the height of the removed vertebra or, respectively, the spacing between the remaining adjacent vertebrae, and on the position of the vertebra in the spine. Therefore, the prior art spinal cage as-semblies generally are adjustable in height. In order to enable adjustments also with the spinal cage assembly of the present invention, it is preferred to provide a second sleeve-shaped member telescopically receiving the first sleeve-shaped member and being of similar shape as the internal sleeve-shaped member. Furthermore, both sleeve-shaped members include bores adapted to be aligned to each other and to receive threaded bolts for holding the two sleeve-shaped members stationary with respect to each other. When in this position the internal sleeve-shaped member pro-jects somewhat from the external sleeve-shaped member. When a pair of bores is provided, two different relative positions may be set. Together with the height of the internal sleeve-shaped member there will result four different heights which will be completely sufficient for most of the cases occurring in practice. The height of the spinal cage assembly is adjusted before the implant is implanted so that difficult manipulations for height adjustment in situ are not required.
According to another aspect of the present invention a force member or the like may be mounted between the sleeve-shaped members telescopically received in each other in order to provide for automatic height adjustment. For example a biased spring may be provided to move the sleeve-shaped members apart from each other when a respective fixing means will be released. Other force members may be used.
While the sleeve-shaped member may be of square or polygonal cross section, the circular cross-section in conformity with the contour of the vertebrae is preferred.
As already mentioned the tool for implanting the sleeve-shaped member has a relatively long shank. Such shank may rotatably receive a sleeve at its free end, which sleeve engages a shoulder of the shank and has at its free end a concave recess of a shape conforming to the shape of the external contour of the sleeve-shaped member. In this manner transverse forces to be applied by the tool when the sleeve-shaped member is being implanted, are transferred not only via the relatively thin threaded extension but also via the sleeve.
The invention will be explained in more detail with reference to drawings.
Fig. 1 is a perspective view of a spinal cage assembly according to the inven-tion;
Fig. 2 is a side elevation of the spinal cage assembly of Fig. 1 in a first di-rection;

Fig. 3 is a side elevation of the spinal cage assembly of Fig. 1 in the opposite direction;
Fig. 4 is an elevation of the spinal cage assembly of Fig. 1 in the assembled condition;
Fig. 5 is a side elevation of the internal sleeve-shaped member of the spinal cage assembly of Fig. l;
Fig. 6 shows schematically a tool for handling the spinal cage assembly of Fig. 1;
Fig. 7 shows a detail in Fig. 6;
Fig. 8 is a cross-section of the sleeve of the tool of Fig. 6.
A spinal cage assembly 10 as shown in Figs. 1 to 4 comprises an external sleeve-shaped member 12 and an internal sleeve-shaped member 14. Both sleeve-shaped members 12, 14 have a relative thick wall, are made of a metal compatible with the human body, preferably titanium, and are of a circular cross-section.
The dimensions are such that the sleeve-shaped member 14 is telescopically received in the external sleeve-shaped member 12. Furthermore the diameters of the external sleeve-shaped member 12 and the internal sleeve-shaped member 14 are selected such that the spinal cage assembly is supported substantially against the cortex when it is positioned between adjacent vertebrae. The shown spinal cage assembly is suit-ed primarily for lumbal vertebrae.
The external sleeve-shaped member 12 includes a pair of elongated windows shown at 16 in Figs. 1 and 3. They can be used for inserting bone material.
The external sleeve-shaped member includes further eight radial holes 18 and 20 positioned in pairs one above the other. The holes of one pair are positioned above each other along an axis parallel to the longitudinal axis of the sleeve-shaped member 12. The holes of adjacent pairs 18, 20 are offset with respect to each other as may be best seen in Figs. 2 and 3.
Finally the sleeve-shaped member 12 includes a pair of threaded bores one of which is shown at 22. The purpose of the various holes or bores in the wall of the sleeve-shaped member 12 will be explained in more detail below.

The sleeve-shaped member 12 has at its upper and lower sides circumferen-tially uniformly spaced teeth 24 having flat upper surfaces 26. Gaps 28 of circular arc-shape are provided between the teeth and define together with the teeth relati-vely sharp edges in the area of the upper surfaces 26. Therefore, the upper and lower sides of the sleeve-shaped member prevent rotary movements thereof when it is implanted so as to provide a rotation preventing means.
The internal sleeve-shaped member 14 is of similar shape as member 12 and has upper and lower sides provided with teeth 32 and rounded gaps 34. The internal sleeve-shaped member 14 includes also pairs of windows 36 which are of elongated shape and can be aligned to the windows 16. Furthermore, the internal sleeve-shap-ed member 14 includes four threaded bores positioned in pairs one above each other, of which two pairs 38, 40 may be seen in Fig. 2. The bores of each pair are positioned vertically above each other. The bores of each pair may be aligned to the holes of a pair 18, 20 of the external sleeve-shaped member 12. Two screws or threaded bolts 42, 44 may be inserted into the holes 18 and 20, respectively.
A
smooth portion 46 thereof will be positioned in a hole 18 or, respectively, 20, while a threaded portion 48 may be engaged into the respective threaded bore 38 or 40, respectively, in order to hold the internal and external sleeve-shaped members 14, 12 stationary with respect to each other as shown in Fig. 4. Since the holes or bores of the pairs 18, 20 and, respectively, the pairs 38, 40 are offset with respect to each other in height, different relative positions of the internal and external sleeve-shaped members may be set. When for example the lowest bore of the pair 38 is aligned with the lowest hole of pair 18, the internal sleeve-shaped member 14 projects only slightly from the external sleeve-shaped member 12. When, however, the upper bore of pair 40 is aligned to the upper hole of pair 20, the internal sleeve-shaped member 14 projects maximally from the external sleeve-shaped member 12.
The internal sleeve-shaped member 14 includes further threaded bores 50 of which one is shown in Fig. 1 and two are shown in Fig. 2. The threaded bores serve - in the same manner as threaded bores 22 - for connection with a tool shown in Figs. 6 to 8 as will be explained in more detail below.

The internal sleeve-shaped member 14 has an inclined upper surface as shown in Fig. 3. Fig. 5 shows the internal sleeve-shaped member 14 separately.
As may be seen the upper surface is inclined to a transverse axis under an angle a of 6°
and the lower surface under an angle b of 3°. Depending on which end of the inter-nal sleeve-shaped member 14 is inserted first into the external sleeve-shaped mem-ber, a respective inclination of the upper surface will result. This allows for adapta-tion to respective anatomic geometries.
It will be appreciated that an internal sleeve-shaped member 14 or an external sleeve-shaped member 12 alone may be used.
Figs. 6 to 8 show a suitable assembly tool 52 having a handle 54, a shaft 56 of a length of e.g. 20 cm and an extension 58 of a reduced diameter at the forward end. As is apparent from Fig. 7 the extension 58 has a threaded portion 60 at its free end. A sleeve 62 is mounted on the extension and has a bore with an internal thread-ed portion 64 extending to the left hand end while being spaced from the right hand end. The right hand or free end of the sleeve 62 has a concave recess 66 which is of a shape conforming to the round contour of the internal sleeve-shaped member 14 or the external sleeve-shaped member 12. During assembly, the sleeve 76 is thread-ingly engaged on the threaded portion 60 of the extension 58 and will then have one end engage a respective shoulder 68 of shaft 56. As a result, the sleeve 62 is mount-ed for rotation, however, fixed against axial displacement by the threads and may be removed only by unscrewing. When the tool will be connected to the spinal cage assembly of Figs. 1 to 5, the threaded portion 60 of the extension 58 will be thread-ed into the threaded bore 22 or threaded bore 50, with the sleeve 62 being rotated such that it will matingly engage the external side of the sleeve wall. This allows to transmit forces from shank 56 to the spinal cage assembly.
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Claims

CLAIMS:

1. A spinal cage assembly comprising an external sleeve member and an internal sleeve member both of metal compatible with the human body, the external sleeve member being adapted to telescopically receive the internal sleeve member, the sleeve members having end faces defining irregular edges, the sleeve members including bores or holes to be aligned with each other and to receive threaded bolts for holding the sleeve members stationary with each other in different height positions.

2. The spinal cage assembly of claim 1, wherein at least one irregular edge of at least one of sleeve members is inclined with respect to a transverse axis of the sleeve members under a predetermined angle.

3. The spinal cage assembly of claim 2, wherein the predetermined angle is between 3° and 6°.

4. The spinal cage assembly of any one of claims 1 to 3, wherein the irregular edges are provided with teeth and gaps therebetween.

5. The spinal cage assembly of claim 1, wherein the teeth have tips formed as a planar surface.

6. The spinal cage assembly of claim 4, wherein the gaps are of circular arc shape, the gaps and said planar surfaces defining relatively sharp edges therebetween.

7. The spinal cage assembly of any one of claims 1 to 6, wherein walls of the sleeve members include elongated holes having longitudinal axes substantially parallel to a longitudinal axis of sleeve members.

8. The spinal cage assembly of any one of claims 1 to 7, wherein the wall of the external sleeve member includes at least one threaded bore for receiving a positioning tool which is provided with a threaded extension at a free end thereof.

9. The spinal cage assembly of any one of claims 1 to 8, wherein the external sleeve member includes at least two circumferentially spaced holes, the internal sleeve member includes at least two circumferentially spaced threaded bores adapted to be aligned to radial holes of the external sleeve member such that the internal sleeve member partially projects from the external sleeve member.

10. The spinal cage assembly of claim 9, wherein two or three pairs of radial holes and threaded bores are provided, the holes and, respectively, bores of each pair being disposed above each other along an axis parallel to a longitudinal axis of the external sleeve member or, respectively, internal sleeve member.

11. The spinal cage assembly of any one of claims 1 to 10, wherein a force member acts between the external and internal sleeve member so as to enable adjustment thereof in height, and fixing means are provided to fix the sleeve-shaped members in their respective positions.

12. The spinal cage assembly of any one of claims 1 to 11, wherein the walls of the sleeve members are provided with radial windows.

13. The spinal cage assembly of any one of claims 1 to 12, wherein the external and the internal sleeve members are of circular cross section.

14. The spinal cage assembly of any one of claims 1 to 13, wherein the threaded bolts comprise a head and a stem, the stem comprising a threaded portion and a cylindrical portion arranged between said threaded portion and the head and being of a diameter corresponding substantially to a diameter of the radial holes of the external sleeve member.

15. The combination of a tool and the spinal cage assembly as defined in any one of claims 8 to 14, wherein the tool has an elongated shank having a handle at one end thereof and a threaded extension at the other end.

16. The combination of claim 15, wherein a sleeve is rotatably mounted upon said threaded extension so as to cooperate with a shoulder of said elongated shaft at an end thereof remote from said threaded extension, and includes a concave recess of a shape conforming to the rounded shape of said internal or, respectively, external sleeve-shaped member.

17. The combination as defined in claim 16, wherein said threaded extension includes a smooth portion and said sleeve has an internal threaded portion spaced from a free end thereof, said internal threaded portion being out of engagement with the threads of said threaded extension when said sleeve engages said shoulder.

18. The spinal case assembly as set forth in claim 1, wherein at least one of the internal or external sleeve members has two end faces each of which form a different angle of between about 3° and about 6° with respect to a transverse axis of the sleeve member such that an edge having a different angle as exposed depending on which end of the inner sleeve member is inserted into or through the external sleeve member.

19. A spinal cage assembly according to claim 18, wherein said irregular edges have teeth and gaps between the teeth.

20. A spinal cage assembly according to claim 19, wherein said teeth have tips having flat surfaces.

21. A spinal cage assembly according to claim 20, wherein said gaps between the teeth each form an arc-shaped curve, with the gaps between the teeth forming relatively sharp edges with the flat surfaces.

22. A spinal cage assembly according to claim 21, wherein said holes are elongated and have a longitudinal axis which is approximately parallel to the longitudinal axis of the sleeve member.

23. A spinal cage assembly according to claim 22, wherein at least one threaded hole is provided in said wall for insertion of a positioning tool having a stem having a threaded end.

24. A spinal cage assembly according to claim 18, wherein locking devices are provided to secure together the internal sleeve member and the external sleeve member in their respective positions with respect to each other.

25. A spinal cage assembly according to claim 24, wherein the external sleeve member has at least one radial threaded hole for engagement with a positioning tool having a threaded stem.

26. A spinal cage assembly according to claim 25, wherein said external sleeve member has a wall provided with radial perforations.

27. A spinal cage assembly according to claim 26, wherein the sleeve members have a circular cross section.

28. A spinal cage assembly according to claim 26, wherein said locking devices are threaded screws each having a head and a shaft which has a threaded section, and between the head and the threaded section is provided a cylindrical threadless section whose diameter is approximately the same as the diameter of the radial holes in said external sleeve member.

29. The spinal cage assembly of claim 18, wherein the internal sleeve member is of one-piece construction and the external sleeve member is of one-piece construction, and both sleeve members have substantially the same height.

30. The spinal cage assembly of claim 18, wherein said external sleeve member has at least two radial holes that are offset in the circumferential direction, the internal sleeve member has at least two threaded holes that are offset in the circumferential direction and can be aligned with the radial holes of the external sleeve member in such a way that the internal sleeve member projects partially out of the external sleeve member, and wherein the external sleeve member also has an irregular edge on each end face and threaded screws can be inserted into the holes or and can secure the internal sleeve member and external sleeve member with respect to each other.

31. The spinal cage assembly of claim 30, wherein at least two pairs of radial holes and threaded holes are provided, and wherein the holes of each pair are arranged one above the other along an axis parallel to the longitudinal axis of the respective body.

32. ~The spinal cage assembly of claim 18, wherein locking devices are provided to secure together internal sleeve member and external sleeve member in their respective positions with respect to each other.

33. ~The spinal cage assembly of claim 32, wherein the external sleeve member has at least one radial threaded hole for engagement with a positioning tool having a threaded stem.

34. ~The spinal cage assembly of claim 33, wherein said external sleeve member has a wall provided with radial perforations.

35. ~The spinal cage assembly of claim 34, wherein the sleeve members have a circular cross section.

36. ~The spinal cage assembly of claim 34, wherein said locking devices are threaded screws each having a head and a shaft which has a threaded section, and between the head and the threaded section is provided a cylindrical threadless section whose diameter is approximately the same as the diameter of the radial holes in said external sleeve member.

37. ~A spinal cage assembly comprising an inner sleeve-shaped tubular body which telescopes into or through an outer tubular sleeve-shaped body, each inner and outer sleeve is of one-piece construction made of a physiologically compatible metal, wherein both sleeve-shaped bodies have multiple holes therein, and can be secured at different heights relative to one another, wherein at least one of the sleeve-shaped bodies has two edges which form a different angle of between about 3° and about 6° with respect to the transverse axis of the sleeve-shaped bodies such that an edge having a different angle is exposed depending on which end of said inner body is inserted into or through said outer body.

38. ~A spinal cage assembly according to claim 37, wherein at least one threaded hole is provided in said outer sleeve-shaped body for insertion of a positioning tool having a stem having a threaded end.

39. ~A spinal cage assembly according to claim 37, wherein the inner sleeve-shaped body telescopes into the outer sleeve-shaped body and can be secured therein at different heights with respect to each other.

40. ~A spinal cage assembly according to claim 37, wherein said outer sleeve-shaped body has at least two radial holes that are offset in the circumferential direction, the inner sleeve-shaped body has at least two threaded holes that are offset in the circumferential direction and can be aligned with the radial holes of the outer body in such a way that the inner body projects partially out of the outer body, and wherein the outer body and inner body have end faces with an irregular edge on each end face and threaded screws can be inserted into the holes and can secure the inner body and outer body with respect to each other.

41. A spinal cage assembly according to claim 37, wherein at least two pairs of radial holes and threaded holes are provided, and wherein the holes of each pair are arranged one above the other along an axis parallel to a longitudinal axis of the respective body.

42. A spinal cage assembly according to claim 37, wherein locking devices are provided to secure together inner body and outer body in their respective positions with respect to each other.

14~

43. ~A spinal cage assembly according to claim 42, wherein the inner and outer bodies have a circular cross section.

44. ~A spinal cage assembly according to claim 42, wherein said locking devices are threaded screws each having a head and a shaft which has a threaded section, and between the head and the threaded section is provided a cylindrical threadless section whose diameter is approximately the same as the diameter of the radial holes in said outer sleeve-shaped body.

45. ~The spinal cage assembly of claim 37, wherein both of the inner and outer sleeve-shaped bodies have first and second end faces both forming irregular edges.

46. ~A spinal cage assembly according to claim 37, wherein said sleeve-shaped bodies have circumferential ends with an irregular edge having teeth and gaps between the teeth.